There are many applications for vibration isolators. For example, the suspension system of any vehicle comprises a number of vibration isolators. In particular, a suspension system commonly comprises at least one spring and at least one damper mounted in a suspension structure, which together allow significant movement of a wheel relative to the vehicle so as to isolate the car from vibrations caused by the wheel traveling over an uneven surface.
When a vehicle is moving over a surface, the surface can have irregularities, such as bumps or pot holes, which will cause a wheel of the vehicle to jolt up or down when following the surface. This sudden movement (which is also called a mechanical shock—or shock for short) will be passed directly onto the vehicle, which can cause a lot of discomfort for a person in the vehicle. Typically, a spring is used to absorb shocks by either compressing or extending. This allows the wheel to jolt, which in turn helps the wheel remain in contact with a surface, but also to prevent shocks from being transferred to the body of the vehicle. There are many different types of springs used on vehicles—coil springs, leaf springs, air springs, and torsion bars are some examples of springs used in typical suspension systems.
However, when a spring absorbs a shock it dissipates the energy of the shock through oscillation. On impact it will start to oscillate and continue to oscillate at its resonant frequency until the energy of the shock has been fully dissipated. This oscillation will be transferred to the body of the vehicle and will also reduce the grip a wheel exerts on a surface. In addition, this oscillation can also reduce the stability of the vehicle on the road. In order to control this oscillation, a damper (which is also called a shock absorber) is used. The damper's function is to absorb energy from the spring.
For most road vehicles, the shocks of greatest magnitude are received along a vector which can be predicted (the main shock vector). The spring and damper are mounted along the path of the main shock vector. The largest component of this vector is a vertical component (i.e. perpendicular to the surface of a road). However, not all shocks are received along the main shock vector. For example, when travelling over a bump in a road, the wheel of a vehicle may be pushed by a force comprising a vector perpendicular to the main shock vector. This can result in small shocks and vibrations that cause discomfort, noise, and wear of vehicle parts.
In order to absorb these additional shocks and vibrations, one or more vibration isolating connectors are used. In the context of the present disclosure, a vibration isolating connector is an element comprising one or more resilient materials which is used as an interface in the connection between two parts. Deformation of the vibration isolating connector allows a small amount of movement between the two parts. This in turns allows the vibration isolating connector to absorb small shocks and vibrations. Thus, vibration isolating connectors are particularly useful as part of the connection between elements of the shock absorber structure. A vibration isolating connector can also be used for the same purpose as part of an engine mount to minimize the amount of vibration, which is transferred from the engine of a vehicle to the chassis of the vehicle. In addition a vibration isolating connector can be used to mount the chassis of a vehicle onto the frame of a vehicle to minimize the amount of vibration, which is transferred from the frame of a vehicle to the chassis of the vehicle.
A common type of vibration isolating connector is a bushing. A bushing can be formed comprising any suitable resilient material. For example, rubber and polyurethane are both commonly used. In addition, a bushing can comprise a fluid. The fluid is preferably allowed to pass from one chamber to another via a channel. This type of bushing is known as a hydrobush.
Unfortunately, vibration isolating connectors degrade with use and over time. Degradation of vibration isolating connectors may reduce the performance of a suspension system and can potentially leave the vehicle dangerous to drive. At present, vibration isolating connectors are merely visually inspected to decide if they should be replaced. However, there are several problems with visual inspection.
For example, a skilled person, such as a mechanic must perform the visual test. As a result, the visual test can only be performed periodically and at a cost to the vehicle owner/user. There may be a risk that a vibration isolating connectors can fail between tests, resulting in the vehicle being used in a compromised state until the next test—which increases the wear on the suspension system as a whole and in turn reduces the life span of other components in the suspension system.
In addition, the visual test is performed on a static vehicle. As a result, any problems that only manifest when a vibration isolating connector is under load and the vehicle is moving will not be detected. Furthermore, the visual test may not pick up any internal damage to the vibration isolating connector and is likely to be overly concerned with superficial exterior damage. As a result, a vibration isolating connector with internal damage may be left in place, compromising the performance of the suspension system. Vibration isolating connectors will also be replaced unnecessarily because its surface looks to be in poor condition, even if the bushing has plenty of working life left.
Another drawback may be that a suspension system can comprise a large number of vibration isolating connectors and other parts, some of which may be difficult to visually inspect. Thus, when a driver notices a handling issue or excessive vibration within the chassis and takes the vehicle for inspection, it can be difficult to diagnose the exact problem or determine which vibration isolating connector is the source of the problem. As a result, there is an increased risk of the failure of vibration isolating connectors being misdiagnosed in a test.